Low voltage outdoor lighting systems typically include several components. Among these components are an electrical transformer for converting standard household alternating current into low voltage (typically 12 volts) alternating current. Such systems also utilize various lighting fixtures which are typically mounted above ground and include sockets for low voltage electrical lamps and lenses for refracting light emitted by the lamp. The light fixtures are typically mounted or placed in the ground some distance from the power transformer which is typically located or mounted on the side of the home. The lighting fixutres are connected to, and supplied with electric current from, the transformer by a series of main and smaller feeder electrical cables that run underground from the transformer location to the various light fixture locations. In some cases, the lighting fixtures are connected, physically and electrically, directly to the main cable without any feeder cable running between the lighting fixture and the main cable. In those cases, the light fixture has means incorporated in it for directly connecting to the main cable.
Typically, one main cable runs from the transformer to the ground area where the lighting fixtures are placed. This main cable is relatively large as it must carry the total current for the sum of the lighting fixtures. However, smaller cables, that is, cables with smaller diameter conductors and insulators, are typically run from the main cable to the lighting fixture since these cables only carry current for one lamp. The cable from the lamp to the main cable is connected to the main cable by a connecting device, hereinafter called "cable connector," which physically joins the two cables to each other and also forms an electrical connection between the main cable and the cable running to the fixture. Each light fixture's feeder cable must be connected to the main cable by a cable connector.
Cable connectors are also utilized wherever it is desirable to add an additional length of main cable to the existing main cable. Additional main cable would be required whenever one wanted to add light fixtures at a location more distant from the power transformer or if one wanted to add additional light fixtures in the same area as the first set of fixtures by utilizing a "parallel" electrical circuit. The two sections of main cable would be joined by a cable connector which would physically and electrically connect the two lengths of main cable.
Since low voltage outdoor lighting systems are typically sold to consumers-homeowners who, in turn, usually install the systems themselves, it is highly desirable that the components and systems are capable of being assembled and installed with ease. The cable connectors utilized in such systems are no exception. The connections between the main and feeder cables, and between the main cables, must be capable of being completed with ease. Accordingly, cable connectors must be designed to provide reliable physical and electrical connections that can be accomplished with ease by the typical consumer-homeowner.
The majority of connectors utilized in low voltage outdoor lighting systems are of the insulation displacement type. Typical insulation displacement type connectors for low voltage lighting systems physically and electrically join two cables by utilizing a clamping type connector that incorporates electrically conductive jumper strips with integral sharp protrusions. The sharp protrusions on the jumper strips pierce through the usually soft insulating material surrounding the electrically conductive core material of the cable. The protrusions pierce through the insulating material when a clamping force is applied, by the system installer, to the two halves of the cable connector, between which lie the cables to be physically and electrically connected. The cables typically are set in channel-shaped cavities, often called cable guide channels, formed in one side of the connector wherein the cavities are sized so as to accept a particular size cable. The electrically conductive jumper strips are typically fixed upon one-half of the connector facing the cables to be clamped between the halves. The strips are fixed in position so as to both mechanically grip the cables being connected and to also electrically connect them. The mechanical connection is made by the piercing, caused by the above-mentioned clamping force transmitted to the sharp protrusions on the jumper strips, of the cable's insulating materials that surround the cable's conductive core. The electrical connection is accomplished when the clamping force transmitted to the two halves of the clamp and, thus, the jumper strips, is increased to the degree where the sharp protrusions of the integral jumper strips pierce through the insulating material and physically contact the electrically conductive core of the cable. The jumper strips, each having two sharp protrusions, are placed within the clamp halves so that the strip's protrusions engage, pierce and contact the core of the proper portions of the cables to be joined. Since each main feeder cable has an electrically charged ("hot") and neutral side to it, it is important that the jumper strips be placed and fixed on the cable connector so that the strips mechanically and electrically connect the "hot" side of the main cable to one side of the other cable and the neutral side of the main cable to the other side of the other cable. The proper alignment between the base and the cap as well as the location of the jumper strips and the corresponding channels for accepting the cables in the mating base are requisites for proper alignment of the jumper strip protrusions with the corresponding cable conductors of the cables being connected.
Various types of insulation displacement connectors have been utilized in the low voltage outdoor lighting industry to date. Each has presented problems while attempting to achieve the requisite proper alingment and clamping discussed above. Some clamps utilize a design wherein the operator must directly press the cables onto the sharp protrusions of the jumper strips so as to ensure proper alignment of the strip protrusions with the conductive core of the cable. Such a design creates obvious problems as there is no assurance or guide for proper alignment of the cable. Furthermore, the operator must exert a great deal of force directly on the cable itself without the aid of a mechanical advantage such as is developed in a typical fastener system. The large amount of force mentioned above is required so that the protrusions of the jumper strips will pierce the insulation of the cable to the point of positively, physically connecting the cables and also electrically connecting the cables through the contact of the jumper strips with the conductive cores of both cables.
Another problem encountered in previous cable connector designs arises out of the incorporation of fastening means such as a nut and machine screw combination. In such designs, the two halves of the cable connectors are designed with holes in them for accommodating the nut and machine screw fastening system. The machine screw is placed through the holes of the two cable connector halves after the cables have been aligned and placed between the halves. The nut is then placed on the machine screw and the fastener is then tightened to develop clamping force for drawing the two halves together and forcing the sharp protrusions of the jumper elements through the insulating material of the cables positioned between the connector halves. This design presents problems, though, since it is quite difficult to work with the extremely small nut and machine screw system that is typically utilized on these small cable connectors. The nut is especially prone to falling away from the connector and the installer's hands as he attempts to thread the nut onto the threaded machine screw.
Another problem with the nut and bolt system is that it is often difficult to get the nut properly started onto the threads of the machine screw due to the extremely small hardware and thread pitch used. Furthermore, the utilization of multiple fastener components adds cost to the connector as well as problems with handling and packaging.
Another problem encountered with previous cable connector designs is that the cable connectors are typically designed so as to incorporate only one fixed set of cable guide channels, which means that the cable connector can only accommodate one set of cable sizes. This, of course, means that one cable connector would be used when joining two identical size cables such as 16 gauge to 16 gauge, while a different cable connector would have to be used when connecting non-identical cables such as 16 gauge to 18 gauge.
The present invention addresses the problems associated with prior art cable connectors. In particular, a preferred cable connector according to the present invention accommodates ease of connecting low voltage electrical cables in that it incorporates a fastening means not requiring a nut and machine screw system; means for accommodating varying cable sizes, all within the same connector; and cable alignment means wherein the operator need not directly press, with great force, the cable onto the electrically conductive jumper strips.